Appendix VI. 1207 small cylindrical chamber D is connected at bottom to a point just under the delivery valve, and at top to the air vessel. The rise and fall of water in B acts as a liquid piston to draw in air at E and deliver it into the air vessel, while cock A adjusts the action, c and i> are glass gauges. Jl/ir Y 1062. P. T28 The Centrifugal Pump.—The diagram of pump efficiencies, p. 734, shews that a single pump is unfit for high lifts because of the rapidly decreasing economy at »««*<* pressure. The difficuky can be overcome by compounding that Iplacing two or more pumps m series, so that the pressure-head obtSSd finally is the aggregate of those due to each^purnp.